Robots are being used not only in industries but also increasingly in homes, offices, and the like to assist in chores. Representative examples of such robots used in homes and offices include cleaning robots, guide robots, and security robots. These robots typically carry out their unique functions while moving in a given space.
A mobile robot may include an attitude sensor sensing the attitude of the mobile robot. Here, the ‘attitude’ denotes the position and direction angle of the mobile robot. For example, the attitude of a mobile robot moving on a flat surface may be the two-dimensional position and direction angle of the mobile robot. To estimate the attitude of such a mobile robot, a gyro sensor, an acceleration sensor, and an encoder may be used.
A gyro sensor is a sensor sensing the angular velocity of an object. It measures the rotational angular velocity of an object or a navigating object and may also be referred to as a gyroscope. Gyro sensors can be applied in, for example, handshake compensation devices of camcorders, three-dimensional mouses, attitude controllers of remote control (RC) helicopters, electronic stability program (ESP) of vehicles, and inertial navigation systems of airplanes.
Conventional gyro sensors are used in high-precision navigation systems such as airplanes and offensive or defensive devices with related to weapons. Since these conventional gyro sensors are used in high-precision navigating systems, their various types of errors are not such a problem.
However, low-priced gyro sensors manufactured using micro-electro-mechanical system (MEMS) technology have relatively lower performance than conventional high-priced gyro sensors. Therefore, the performance of gyro sensors manufactured using the MEMS technology needs to be improved.
FIG. 1 is a diagram illustrating theoretical values output from a conventional gyro sensor when a mobile apparatus equipped with the gyro sensor is stationary. Referring to FIG. 1, the gyro sensor is a sensor measuring the rotational angular velocity of an object. Thus, when the mobile apparatus (e.g., a cleaning mobile robot) equipped with the gyro sensor is not rotating, the gyro sensor outputs a constant value since the rotational angular velocity of the mobile apparatus is zero. This constant output value is referred to as a ‘bias value.’
FIG. 2 is a diagram illustrating an output value of a conventional gyro sensor over time when a mobile apparatus equipped with the gyro sensor is rotating. Referring to FIG. 2, when the mobile apparatus is rotating, its angular velocity is not zero. Therefore, the rotational angular velocity of the mobile apparatus may be measured by subtracting a bias value from an output value of the gyro sensor.
Since the rotational angular velocity of a mobile apparatus is sensed based on a bias value and an output value of a gyro sensor, the bias value needs to be estimated relatively accurately. In addition, a method and apparatus for correcting, in real time, a bias value using output values of a gyro sensor are required to relatively accurately estimate the attitude of a mobile robot equipped with the gyro sensor.